Detecting, quantifying, and/or classifying seizures using multimodal data

ABSTRACT

A method, comprising receiving at least one of a signal relating to a first cardiac activity and a signal relating to a first body movement from a patient; triggering at least one of a test of the patient&#39;s responsiveness, awareness, a second cardiac activity, a second body movement, a spectral analysis test of the second cardiac activity, and a spectral analysis test of the second body movement, based on at least one of the signal relating to the first cardiac activity and the signal relating to the first body movement; determining an occurrence of an epileptic event based at least in part on said one or more triggered tests; and performing a further action in response to said determination of said occurrence of said epileptic event. Further methods allow classification of epileptic events. Apparatus and systems capable of implementing the method.

This application is a continuation application of U.S. patentapplication Ser. No. 13/776,176, filed Feb. 25, 2013, which is acontinuation of U.S. patent application Ser. No. 13/098,262, filed Apr.29, 2011 and issued as U.S. Pat. No. 8,382,667 on Feb. 26, 2013. U.S.patent applications Ser. Nos. 13/776,176 and 13/098,262 are herebyincorporated herein by reference in their entireties.

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates to medical device systems and methods capable ofdetecting and, in some embodiments, treating an occurring or impendingseizure using multimodal body data.

INCORPORATION BY REFERENCE

The following United States patents or patent applications areincorporated by reference:

-   U.S. patent application Ser. No. 12/756,065, filed Apr. 7, 2010.-   U.S. patent application Ser. No. 12/770,562, filed Apr. 29, 2010.-   U.S. patent application Ser. No. 12/884,051, filed Sep. 16, 2010.-   U.S. patent application Ser. No. 12/896,525, filed Oct. 1, 2010.-   U.S. patent application Ser. No. 13/040,996, filed Mar. 4, 2011.

Description of the Related Art

Of the approximately 60 million people worldwide affected with epilepsy,roughly 23 million people suffer from epilepsy resistant to multiplemedications. In the USA alone, the annual cost of epilepsy care is USD12 billion (in 1995 dollars), most of which is attributable to subjectswith pharmaco-resistant seizures. Pharmaco-resistant seizures areassociated with an increase mortality and morbidity (e.g., compared tothe general population and to epileptics whose seizures are controlledby medications) and with markedly degraded quality of life for patients.Seizures may impair motor control, responsiveness to a wide class ofstimuli, and other cognitive functions. The sudden onset of a patient'simpairment of motor control, responsiveness, and other cognitivefunctions precludes the performance of necessary and even simple dailylife tasks such as driving a vehicle, cooking, or operating machinery,as well as more complex tasks such as acquiring knowledge andsocializing.

Therapies using electrical currents or fields to provide a therapy to apatient (electrotherapy) are beneficial for certain neurologicaldisorders, such as epilepsy. Implantable medical devices have beeneffectively used to deliver therapeutic electrical stimulation tovarious portions of the human body (e.g., the vagus nerve) for treatingepilepsy. As used herein, “stimulation,” “neurostimulation,”“stimulation signal,” “therapeutic signal,” or “neurostimulation signal”refers to the direct or indirect application of an electrical,mechanical, magnetic, electro-magnetic, photonic, acoustic, cognitive,and/or chemical signal to an organ or a neural structure in thepatient's body. The signal is an exogenous signal that is distinct fromthe endogenous electro-chemical activity inherent to the patient's bodyand also from that found in the environment. In other words, thestimulation signal (whether electrical, mechanical, magnetic,electro-magnetic, photonic, acoustic, cognitive, and/or chemical innature) applied to a cranial nerve or to other nervous tissue structurein the present invention is a signal applied from a medical device,e.g., a neurostimulator.

A “therapeutic signal” refers to a stimulation signal delivered to apatient's body with the intent of treating a medical condition through asuppressing (e.g., blocking) or modulating effect to neural tissue. Theeffect of a stimulation signal on neuronal activity may be suppressingor modulating; however, for simplicity, the terms “stimulating”,suppressing, and modulating, and variants thereof, are sometimes usedinterchangeably herein. In general, however, the delivery of anexogenous signal itself refers to “stimulation” of an organ or a neuralstructure, while the effects of that signal, if any, on the electricalactivity of the neural structure are properly referred to as suppressionor modulation.

Depending upon myriad factors such as the history (recent and distant)of a patient's brain activity (e.g., electro-chemical, mental,emotional), stimulation parameters and time of day, to name a few, theeffects of stimulation upon the neural tissue may be excitatory orinhibitory, facilitatory or disfacilitatory and may suppress, enhance,or leave unaltered neuronal activity. For example, the suppressingeffect of a stimulation signal on neural tissue would manifest as theblockage of abnormal activity (e.g., epileptic seizures) see Osorio etal., Ann Neurol 2005; Osorio & Frei IJNS 2009) The mechanisms thoroughwhich this suppressing effect takes place are described in the foregoingarticles. Suppression of abnormal neural activity is generally athreshold or suprathreshold process and the temporal scale over which itoccurs is usually in the order of tens or hundreds of milliseconds.Modulation of abnormal or undesirable neural activity is typically a“sub-threshold” process in the spatio-temporal domain that may summateand result under certain conditions, in threshold or suprathresholdneural events. The temporal scale of modulation is usually longer thanthat of suppression, encompassing seconds to hours, even months. Inaddition to inhibition or dysfacilitation, modification of neuralactivity (e.g., wave annihilation) may be exerted through collision withidentical, similar or dissimilar waves, a concept borrowed from wavemechanics, or through phase resetting (Winfree).

In some cases, electrotherapy may be provided by implanting anelectrical device, e.g., an implantable medical device (IMD), inside apatient's body for stimulation of a nervous tissue, such as a cranialnerve. Generally, electrotherapy signals that suppress or modulateneural activity are delivered by the IMD via one or more leads. Whenapplicable, the leads generally terminate at their distal ends in one ormore electrodes, and the electrodes, in turn, are coupled to a targettissue in the patient's body. For example, a number of electrodes may beattached to various points of a nerve or other tissue inside a humanbody for delivery of a neurostimulation signal.

While contingent (also referred to as “closed-loop,” “active,” or“feedback” stimulation; i.e., electrotherapy applied in response tosensed information, such as heart rate) stimulation schemes have beenproposed, non-contingent, programmed periodic stimulation is theprevailing modality. For example, vagus nerve stimulation for thetreatment of epilepsy usually involves a series of grouped electricalpulses defined by an “on-time” (such as 30 sec.) and an “off-time” (suchas 5 min.). This type of stimulation is also referred to as “open-loop,”“passive,” or “non-feedback” stimulation. Each sequence of pulses duringan on-time may be referred to as a “pulse burst.” The burst is followedby the off-time period in which no signals are applied to the nerve.During the on-time, electrical pulses of a defined electrical current(e.g., 0.5-3.5 milliamps) and pulse width (e.g., 0.25-1.0 milliseconds)are delivered at a defined frequency (e.g., 20-30 Hz) for a certainduration (e.g., 10-60 seconds). The on-time and off-time parameterstogether define a duty cycle, which is the ratio of the on-time to thesum of the on-time and off-time, and which describes the fraction oftime that the electrical signal is applied to the nerve.

In VNS, the on-time and off-time may be programmed to define anintermittent pattern in which a repeating series of electrical pulsebursts are generated and applied to a cranial nerve such as the vagusnerve. The off-time is provided to minimize adverse effects and conservepower. If the off-time is set at zero, the electrical signal inconventional VNS may provide continuous stimulation to the vagus nerve.Alternatively, the off time may be as long as one day or more, in whichcase the pulse bursts are provided only once per day or at even longerintervals. Typically, however, the ratio of “off-time” to “on-time” mayrange from about 0.5 to about 10.

In addition to the on-time and off-time, the other parameters definingthe electrical signal in VNS may be programmed over a range of values.The pulse width for the pulses in a pulse burst of conventional VNS maybe set to a value not greater than about 1 msec, such as about 250-500μsec, and the number of pulses in a pulse burst is typically set byprogramming a frequency in a range of about 20-300 Hz (i.e., 20 pulsesper second to 300 pulses per second). A non-uniform frequency may alsobe used. Frequency may be altered during a pulse burst by either afrequency sweep from a low frequency to a high frequency, or vice versa.Alternatively, the timing between adjacent individual signals within aburst may be randomly changed such that two adjacent signals may begenerated at any frequency within a range of frequencies.

Although neurostimulation has proven effective in the treatment of anumber of medical conditions, it would be desirable to further enhanceand optimize neurostimulation-based therapy for this purpose. Forexample, it may be desirable to detect an occurring or impendingseizure. Such detection may be useful in triggering a therapy,monitoring the course of a patient's disease, or the progress of his orher treatment thereof. Alternatively or in addition, such detection maybe useful in issuing a warning of an impending or on-going seizure. Sucha warning may, for example, minimize the risk of injury or death. Saidwarning may be perceived by the patient, a physician, a caregiver, or asuitably programmed computer and allow that person or computer programto take action intended to reduce the likelihood, duration, or severityof the seizure or impending seizure, or to facilitate further medicaltreatment or intervention for the patient. In particular, detection ofan occurring or impending seizure enables the use of contingentneurostimulation. The state of the art does not provide an efficient andeffective means for performing such detection and/or warning.Conventional VNS stimulation as described above does not detectoccurring or impending seizures.

Closed-loop neurostimulation therapies for treating epilepsy have beenproposed in which stimulation is triggered based upon factors includingEEG activity (see, e.g., U.S. Pat. Nos. 5,995,868 and 7,280,867) as wellas cardiac-based activity (see., e.g., U.S. Pat. Nos. 6,961,618 and5,928,272). EEG- or ECoG-based approaches involving recording of neuralelectrical activity at any spatio-temporal scale involve determinationof one or more parameters from brain electrical activity that indicate aseizure. Such approaches have met with limited success and have a numberof drawbacks, including highly invasive and technically demanding andcostly surgery for implanted systems. Approaches that do not invade thebrain have marked limitations due mainly to the extremely low/unreliableS/N, and poor patient compliance with, e.g., the patient wearingelectrodes on the scalp for extended periods.

SUMMARY OF THE INVENTION

In one embodiment, the present invention provides a method. In oneembodiment, the method comprises receiving at least one of signalrelating to a first cardiac activity from a patient and a signalrelating to a first body movement from the patient; deriving at leastone patient index from said at least one received signal; triggering atleast one of a test of the patient's responsiveness, a test of thepatient's awareness, a test of a second cardiac activity of the patient,a test of a second body movement of the patient, a spectral analysistest of a second cardiac activity of the patient, and a spectralanalysis test of the second body movement of the patient, based on saidat least one patient index; determining an occurrence of an epilepticevent based at least in part on the one or more triggered tests; andperforming a further action in response to the determination of theoccurrence of the epileptic event.

In one embodiment, the present invention provides a method. In oneembodiment, the method comprises receiving at least two body signalsselected from the group consisting of a signal relating to a first bodymovement, a signal relating to a first cardiac activity, aresponsiveness signal, an awareness signal, a signal relating to asecond cardiac activity, a signal relating to a second body movement, aspectral analysis signal relating to the second cardiac activity, and aspectral analysis signal relating to the second body movement;determining an occurrence of a generalized tonic-clonic epilepticseizure, the determination being based upon the correlation of at leasttwo features, at least one feature being of each of the at least twobody signals, wherein: the feature of the first cardiac activity signalis an increase in the patient's heart rate above an interictal referencevalue; the feature of the first body movement signal is at least one of(i) an increase in axial or limb muscle tone substantially above aninterictal or exercise value for the patient, (ii) a decrease in axialmuscle tone in a non-recumbent patient, below the value associated witha first, non-recumbent position, (iii) fall followed by an increase inbody muscle tone, or (iv) a fall followed by generalized body movements;the feature of the responsiveness signal is a decrease in the patient'sresponsiveness below an interictal reference value; the feature of theawareness signal is a decrease in the patient's awareness below aninterictal reference value; the feature of the second cardiac activitysignal is a correlation with an ictal cardiac activity reference signal;the feature of the second body movement signal is a correlation with anictal body movement reference signal; the feature of the spectralanalysis signal of the second cardiac activity is a correlation with anictal cardiac activity spectral analysis reference signal; or thefeature of the spectral analysis signal of the second body movement is acorrelation with an ictal body movement spectral analysis referencesignal; and performing a further action in response to the determinationof the occurrence of the epileptic event.

In one embodiment, the present invention provides a method. In oneembodiment, the method comprises receiving at least two body signalsselected from the group consisting of a signal relating to a first bodymovement, a signal relating to a first cardiac activity, aresponsiveness signal, an awareness signal, a signal relating to asecond cardiac activity, a signal relating to a second body movement, aspectral analysis signal relating to the second cardiac activity, andspectral analysis signal relating to the second body movement; anddetermining an occurrence of a partial epileptic seizure based upon acorrelation of two features, at least one feature being of each of theat least two body signals, wherein: the feature of the first cardiacsignal is a value outside an interictal reference value range; thefeature of the first body movement signal is a body movement associatedwith a partial seizure; the feature of the second cardiac activitysignal is a correlation with an ictal cardiac activity reference signal;the feature of the second body movement signal is a correlation with anictal body movement reference signal; the feature of the spectralanalysis signal of the second cardiac activity is a correlation with anictal cardiac activity spectral analysis reference signal; or thefeature of the spectral analysis signal of the second body movement is acorrelation with an ictal body movement spectral analysis referencesignal; and performing a further action in response to the determinationof the occurrence of the epileptic event.

In other embodiments, a computer readable program storage device isprovided that is encoded with instructions that, when executed by acomputer, perform a method described above.

In one embodiment, a medical device is provided comprising an autonomicsignal module, a kinetic signal module, a detection module, and aprocessor adapted to perform a method as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be understood by reference to the followingdescription taken in conjunction with the accompanying drawings, inwhich like reference numerals identify like elements, and in which:

FIG. 1 provides stylized diagrams of medical devices. FIG. 1A shows anexternal device in communication with a sensor. FIG. 1B shows animplanted device providing a therapeutic signal to a structure of thepatient's body, each in accordance with one illustrative embodiment ofthe present invention;

FIG. 2 provides a block diagram of a medical device system that includesa medical device and an external unit, in accordance with oneillustrative embodiment of the present invention;

FIG. 3A provides a block diagram of a cardiac signal module of a medicaldevice, in accordance with one illustrative embodiment of the presentinvention;

FIG. 3B provides a block diagram of a kinetic signal module of a medicaldevice, in accordance with one illustrative embodiment of the presentinvention;

FIG. 3C provides a block diagram of a detection module of a medicaldevice, in accordance with one illustrative embodiment of the presentinvention;

FIG. 4 shows the time of appearance (relative to clinical onset, dashedvertical line) and direction of deviations from reference activity of aplurality of body signals for four seizure types, specifically, absenceseizures, tonic-clonic seizures, and simple or complex partial seizures;

FIG. 5 shows time courses (relative to clinical onset, dashed verticalline) of activity of a plurality of body signals for tonic-clonicseizures;

FIG. 6 shows time courses (relative to clinical onset, dashed verticalline) of activity of a plurality of body signals for partial (simple orcomplex) seizures; FIG. 7 shows time courses (relative to clinicalonset, dashed vertical line) of activity of a plurality of body signalsfor idiopathic absence seizures;

FIG. 8 shows (A) an exemplary two-dimensional plot of a trajectory ofepileptic movements, (B) an exemplary three-dimensional plot ofepileptic movements, and (C) an additional exemplary three-dimensionalplot of epileptic movements;

FIG. 9 shows three two-dimensional, temporally cumulative plots ofdiscrete movements during the clonic phase of a primarily or secondarilygeneralized tonic-clonic seizure;

FIG. 10 shows a flowchart of an implementation of a method according toone embodiment of the present invention;

FIG. 11 shows a flowchart of an implementation of a method according toone embodiment of the present invention; and

FIG. 12 shows a flowchart of an implementation of a method according toone embodiment of the present invention.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and are herein described in detail. It shouldbe understood, however, that the description herein of specificembodiments is not intended to limit the invention to the particularforms disclosed, but on the contrary, the intention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the invention as defined by the appended claims.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Illustrative embodiments of the invention are described herein. In theinterest of clarity, not all features of an actual implementation aredescribed in this specification. In the development of any such actualembodiment, numerous implementation-specific decisions must be made toachieve the design-specific goals, which will vary from oneimplementation to another. It will be appreciated that such adevelopment effort, while possibly complex and time-consuming, wouldnevertheless be a routine undertaking for persons of ordinary skill inthe art having the benefit of this disclosure.

This document does not intend to distinguish between components thatdiffer in name but not function. In the following discussion and in theclaims, the terms “including” and “includes” are used in an open-endedfashion, and thus should be interpreted to mean “including, but notlimited to.” Also, the term “couple” or “couples” is intended to meaneither a direct or an indirect electrical connection. “Direct contact,”“direct attachment,” or providing a “direct coupling” indicates that asurface of a first element contacts the surface of a second element withno substantial attenuating medium there between. The presence of smallquantities of substances, such as bodily fluids, that do notsubstantially attenuate electrical connections does not vitiate directcontact. The word “or” is used in the inclusive sense (i.e., “and/or”)unless a specific use to the contrary is explicitly stated.

The term “electrode” or “electrodes” described herein may refer to oneor more stimulation electrodes (i.e., electrodes for delivering atherapeutic signal generated by an IMD to a tissue), sensing electrodes(i.e., electrodes for sensing a physiological indication of a state of apatient's body), and/or electrodes that are capable of delivering atherapeutic signal, as well as performing a sensing function.

Identification of changes in brain state are generally described in U.S.patent application Ser. No. 12/896,525, filed Oct. 1, 2010, incorporatedherein by reference. As stated therein, implanted sensors or electrodesbeneath the scalp but above the outer skull table or intra-cranial(epidural, subdural or depth) have been used to overcome the limitationsof scalp recordings. However, the quality of data is limited; there arerisks (e.g., infection, bleeding, brain damage) associated with thesedevices; and in addition, at this time, there are at most about 300neurosurgeons capable of implanting intracranial electrodes, far too fewto perform such implantation for the roughly 900,000 pharmaco-resistantepileptics in the United States.

The basis for our work in using multimodal signals for detection ofstate changes in the brain is as generally described in U.S. patentapplication Ser. No. 12/896,525, filed Oct. 1, 2010. Various multimodalsignals that may be used in the invention are set forth in the followingtable:

TABLE 1 Multimodal Signals Autonomic Cardiac: EKG, PKG,Echocardiography, Apexcardiography (ApKG), Intra-cardiac pressure,Cardiac blood flow, cardiac thermography; from which can be derived,e.g., heart rate (HR), change of HR, rate of change of HR, heart rhythm,changes in heart rhythm, heart rate variability (HRV), change of HRV,rate of change of HRV, HRV vs. HR. Also, heart morphology (e.g., size)blood pressure (arterial and venous), heart sounds,, heartbeat wavemorphology, heartbeat complex morphology, and magnitude and shape ofthoracic wall deflection. Vascular: Arterial Pressure, Arterial andvenous blood wave pressure morphology; Arterial and venous blood flowvelocity and degree of turbulence, arterial and venous blood flowsounds, arterial and venous temperature Respiratory: Frequency, tidalvolume, minute volume, respiratory wave morphology, respiratory sounds,end-tidal CO2, Intercostal EMG, Diaphragmatic EMG, chest wall andabdominal wall motion, from which can be derived, e.g.,, respirationrate (RR), change of RR, rate of change of RR, respiratory rhythm,morphology of breaths. Also, arterial gas concentrations, includingoxygen saturation, as well as blood pH can be considered respiratorysignals. Dermal: Skin resistance, skin temperature, skin blood flow,sweat gland activity Concentrations of catecholamines (and theirmetabolites) and acetylcholine or acetylcholinesterase activity inblood, saliva and other body fluids concentrations and its rate ofchange. Neurologic Cognitive/behavioral: Level of consciousness,attention, reaction time, memory, visuo- spatial, language, reasoning,judgment, mathematical calculations, auditory and/or visualdiscrimination Kinetic: Direction, speed/acceleration, trajectory (1D to3D), pattern, and quality of movements, force of contraction, bodyposture, body orientation/position, body part orientation/position inreference to each other and to imaginary axes, muscle tone,agonist-to-antagonist muscle tone relation, from which can be derived,e.g., information about gait, posture, accessory movements, fallsVocalizations: Formed, unformed EEG/ECoG, Evoked potentials, fieldpotentials, single unit activity Endocrine: Prolactin, luteinizinghormone, follicle stimulation hormone, growth hormone, ACTH, cortisol,vasopressin, beta-endorphin, beta, lipotropin-, corticotropin- releasingfactor (CRF) Stress Markers: CK, troponin, reactive oxygen and nitrogenspecies including but not limited to iso- and neuro-prostanes andnitrite/nitrate ratio, gluthatione, gluthatione disulfide andgluthatione peroxidase activity, citrulline, protein carbonyls,thiobarbituric acid, the heat shock protein family, catecholamines,lactic acid, N-acetylaspartate, and metabolites of any of the foregoing.Metabolic: arterial pH and gases, lactate/pyruvate ratio, electrolytes,glucose

Terms such as “epileptic event” and “reference value,” among others,have been defined in U.S. patent application Ser. No. 12/896,525, filedOct. 1, 2010. “Interictal” refers to a period after a post-ictal periodand before a pre-ictal period.

FIGS. 4-7 have been substantially fully described in U.S. patentapplication Ser. No. 12/896,525, filed Oct. 1, 2010.

Various features of signals for various types of seizures are alsogenerally described in U.S. patent application Ser. No. 12/896,525,filed Oct. 1, 2010.

U.S. patent application Ser. No. 12/896,525, filed Oct. 1, 2010 alsodiscusses methods capable of distinguishing epileptic generalized fromnon-epileptic generalized or “convulsive” seizures whose kineticactivity, but not patho-physiology, resembles that of epilepticseizures.

The selectivity (Sl), sensitivity (Se) and specificity (Sp) of varioussignal features are generally described in U.S. patent application Ser.No. 12/896,525, filed Oct. 1, 2010. U.S. patent application Ser. No.12/896,525 also discusses consideration of these and other signalfeatures in determining optimal signal(s) for use in detection ofepileptic events in a particular patient, of a particular type, or thelike.

A Positive Predictive Value (PPV) of a signal or combination of signalsis generally described in U.S. patent application Ser. No. 12/896,525,filed Oct. 1, 2010. The person of ordinary skill in the art will alsounderstand a Negative Predictive Value (NPV) of a signal, defined as:(number of True Negatives)/number of True Negatives+number of FalseNegatives.

In one embodiment, the present invention relates to a method, comprisingreceiving at least one of a signal relating to a first cardiac activityfrom a patient and a signal relating to a first body movement from thepatient; deriving at least one patient index from said at least onereceived signal; triggering at least one of a test of the patient'sresponsiveness, a test of the patient's awareness, a test of a secondcardiac activity of the patient, a test of a second body movement of thepatient, a spectral analysis test of a second cardiac activity of thepatient, and a spectral analysis test of a second body movement of thepatient, based on said at least one patient index; determining anoccurrence of an epileptic event based at least in part on the one ormore triggered tests; and performing a further action in response to thedetermination of the occurrence of the epileptic event.

Cardiac activity signals, as well as techniques for determining them,are generally described in U.S. patent application Ser. No. 12/896,525,filed Oct. 1, 2010.

Body movement (a.k.a kinetic) signals, as well as techniques fordetermining them, are generally described in U.S. patent applicationSer. No. 12/896,525, filed Oct. 1, 2010. It should be borne in mind thatthe terms “body movement” and “kinetic,” as used herein, also encompassthe absence of specific body movements (motionless).

The term, and concept of, “responsiveness” as used in reference to theembodiments described herein, has a motor and a cognitive componentwhich may be strongly correlated or dissociated; further the motorcomponent may be in the form of a simple response (e.g., withdrawal of alimb from a pain source) or complex (e.g. drawing a triangle in responseto a command). Consequently, responsiveness may be tested using simplestimuli (e.g., acoustic in the form of a loud noise or sensory in theform of a pinprick) or complex (e.g., complex reaction time tests;questions probing knowledge, judgment, abstraction, memory, etc.). Inthis invention, when “responsiveness” is tested using complex stimuli,“awareness” is being probed and therefore in that case theseterms/concepts are used interchangeably. The meaning of “responsiveness”is thus, context dependent: if the objective is to determine if apatient generates simple motor responses or movements, the term“responsiveness” may be used and if it is to test the presence andquality of complex responses, “awareness” may replace responsiveness.

As used herein, “spectral analysis” encompasses spectral analyses usingat least one of the known methods (e.g., Fourier-based, wavelet based;multifractal spectral, etc) of cardiac activity or body movements.Spectral analysis techniques are known to the person of ordinary skillin the art and can be implemented by such a person having the benefit ofthe present disclosure. Spectral analysis may be discrete or continuous.Spectral analysis of a cardiac activity can comprise spectral analysisof heart rate or individual beats' EKG complexes, among others.

The patient index can be a value derived directly from the signalrelating to the first cardiac activity or the signal relating to thefirst body movement. For example, one or more heart rate values can bederived from a cardiac activity signal over one or more periods of time.For example, as described in U.S. patent application Ser. No.12/770,562, filed Apr. 29, 2010, a foreground heart rate over arelatively short time period (e.g., 5-30 sec) and a background heartrate over a longer time period (e.g., 30-600 sec) can both be derivedfrom a cardiac activity signal. For another example, an accelerometer orinclinometer mounted on a patient's body can give information about thepatient's (and/or parts of his body) movements and body position, suchas are described in more detail in U.S. patent application Ser. No.12/896,525, filed Oct. 1, 2010.

The patient index can also be a determination of an epileptic event. Forexample, the cardiac activity and/or body movement can be analyzed todetermine an occurrence of an epileptic event, a non-occurrence of anepileptic event, or a probable occurrence of an epileptic event.

In one embodiment, triggering the test(s) can be based on at least oneof a patient's cardiac activity and the patient's body movement upon afinding that the cardiac activity and/or body movement are indicative ofa possible epileptic event. For example, if the cardiac activity and/orbody movement clearly indicate an epileptic event with high confidence,triggering the test(s) need not be performed; but if the cardiacactivity and/or body movement are outside their interictal referencevalue ranges but have values that give only low confidence of anepileptic event, triggering can be performed to provide additionalinformation about the patient's condition to indicate whether he or sheis suffering an epileptic event or not.

For another example, the patient's cardiac activity at a first time mayindicate an epileptic event, and the patient's body movement at a secondtime and in a particular region of the body may indicate an epilepticevent, but if the two times differ, or the body movement is in adifferent region of the body, or changes in their characteristics (e.g.,rate, morphology, pattern, etc.) are discordant with declaring theepileptic event, consideration of cardiac activity and body movement maylead to low confidence of an indication of an epileptic event, and inresponse thereto, triggering of additional test(s) and/or considerationof additional body signals may be desirable. In other words, there maybe a low absolute value of correlation (e.g., a correlation betweenabout −0.4 and 0.4) between the patient's cardiac activity and thepatient's body movement that would prevent highly confidentdetermination of an epileptic event. The triggered test(s) may provideenough additional information to make a highly confident determinationof an epileptic event (or the non-occurrence of an epileptic event).

Generally, two parameters can be considered highly correlated if thecoefficient of correlation is greater than about 0.7, and lowlycorrelated if the coefficient of correlation is less than about 0.4. Twoparameters can be considered highly anticorrelated if the coefficient ofcorrelation is less than about −0.7, and lowly anticorrelated if thecoefficient of correlation is greater than about −0.4. One example ofparameters/situations that can be considered to be anticorrelatedincludes an appearance of tachycardia with a disappearance of bodymovement. Other examples that can be considered to be anticorrelated area strong body movement with either a substantially unchanged heart rateor a decreased heart rate. The example with the substantially unchangedheart rate can be considered a low anticorrelation, and the example withthe decreased heart rate can be considered a high anticorrelation.

Another pair of examples to consider are the correlations between bodymovement and first derivative of heart rate in an epileptic event vs. inexercise. Generally, the first derivative of heart rate is greater in anepileptic event than in exercise, i.e., body movement and the firstderivative of heart rate can be considered more highly correlated inepileptic events than in exercise.

The presence of either high or low correlation or anti-correlations maybe used in this invention to determine the occurrence of an epilepticevent and trigger an action(s) or to determine that an epileptic eventis not occurring or did not occur. The first and second cardiac activitymay be the same (in other words, triggering can be of a second iterationof a test that reported the first cardiac activity as a result of afirst iteration, giving a more current value of the cardiac activity),or they may be different. In one embodiment, the first cardiac activityis heart rate or heart rate variability, and the second cardiac activityis heart beat morphology.

Similarly, the first and second body movement may be the same, or theymay be different.

A “test” is used herein to refer to any assay of the patient's cardiacactivity, body movement, responsiveness, awareness, or a spectralanalysis thereof. The product of a test can be considered a signal, anda signal can be considered as resulting from a test. A test of thesecond cardiac activity may use substantially the same data source, dataprocessing, and/or related techniques as are used in receiving thesignal relating to the first cardiac activity. In another embodiment,the techniques may differ. For example, the first cardiac activity canbe heart beat morphology determined by electrocardiography (EKG), andthe second cardiac activity can be heart beat morphology determined byphonocardiography (PKG).

Similarly, a test of the second body movement may, but need not, usesubstantially the same data source, data processing, and/or relatedtechniques as are used in receiving the signal relating to the firstbody movement.

The concept of first and second cardiac activity or first and secondbody movement is also applicable to responsiveness and awareness. Forexample responsiveness activity may be a reflex movement such aswithdrawal from a source of painful stimuli and a second responsivenessactivity may be a complex movement such as that required to draw atriangle. Different tests of varying levels of complexity may beadministered to test responsiveness as defined in this invention.

The particular triggered test(s) may be selected based at least in parton the first cardiac activity, the first body movement, or both.

In one embodiment, determining is based on at least one of a finding thepatient's awareness differs from a reference responsiveness level, afinding the patient's awareness differs from a reference awarenesslevel, a finding the patient's second cardiac activity includes acharacteristic suggestive of an epileptic event, a finding the spectralanalysis of the patient's second cardiac activity includes acharacteristic suggestive of an epileptic event, and a finding thespectral analysis of the patient's second body movement includes acharacteristic suggestive of an epileptic event.

FIG. 10 shows a flowchart depicting one embodiment of a method accordingto the present invention. A cardiac activity signal indicative of thepatient's cardiac activity is received at block 1010 and/or a bodymovement signal indicative of a body movement of the patient is receivedat block 1020.

Thereafter, a determination is made in block 1030 whether cardiacactivity and body movement are associated with an epileptic event. Ifno, flow returns to the receiving blocks 1010-1020. If yes, an epilepticevent is declared at block 1040. However, if no determination can bemade, flow moves to block 1050, where one or more of a responsivenesstest, an awareness test, a second cardiac activity test, a second bodymovement test, a spectral analysis test of the second cardiac activity,or a spectral analysis test of the second body movement, are triggered.

Thereafter, a determination is made in block 1060 whether the patient'sresponsiveness, awareness, second cardiac activity, second bodymovement, and/or spectral analysis of second cardiac activity or secondbody movement are indicative of an epileptic event. If no, flow returnsto the receiving blocks 1010-1020. If yes, an epileptic event isdeclared at block 1040.

Alternatively or in addition to declaring an epileptic event, furtheractions can be performed. In one embodiment, the method furthercomprises classifying the epileptic event based upon at least one of thefirst cardiac activity, the first body movement, the responsiveness, theawareness, the second cardiac activity, the second body movement, thespectral properties of the second cardiac activity, the spectralproperties of the second body movement, and two or more thereof.

Classifications of epileptic events can be generally based on theinformation shown in FIGS. 4-7 and the discussion herein and in U.S.patent application Ser. No. 12/896,525, filed Oct. 1, 2010.Classifications can also be based in part on observations ofstereotypical seizures of a particular patient. Not all seizures that aclinician would recognize as being of a particular type may exhibit allthe properties discussed herein, and thus, not all may be amenable toclassification by the methods described herein, but a substantialmajority are expected to be amenable to classification by the methodsdescribed herein.

In one embodiment, the epileptic event is classified as a generalizedtonic-clonic seizure when the following occur in a patient in a first,non-recumbent position: the first body movement comprises a fall fromthe first, non-recumbent position, wherein (i) the fall is associatedwith a loss of responsiveness, a loss of awareness, or both; and (ii)the fall is followed by generalized body movements.

Falls to the ground associated with a primarily or secondarilygeneralized tonic-clonic, generalized tonic, generalizedclonic-tonic-clonic seizure or generalized atonic seizure aredistinguishable from those caused by tripping or slipping by the absenceof protective/defensive actions (e.g., breaking the fall with the arms)and other features such which body part(s) is(are) first on contact withthe ground.

Primarily generalized seizures usually result in synchronous bilateralmovements of equal amplitude, with maintenance of head and eyes on themidline. Secondarily generalized seizures usually manifest at onset withunilateral movements of limbs, head, eyes, or trunk.

In one embodiment, the generalized body movement comprises a rhythmicbody movement. Alternatively or additionally, the generalized bodymovements can comprise flexion and extension of joints and/or can have afrequency of about 3 Hz at some time during the epileptic event. Inanother embodiment, the rhythmic movement is temporally associated withan epileptiform discharge.

Body movement can allow classification of an epileptic event as toprimarily generalized or secondarily generalized. Specifically, theepileptic event can be classified as primarily generalized if bodymovements are synchronous and of equal amplitude on both sides of thebody, and as secondarily generalized if not.

In a further embodiment, the epileptic event is classified as ageneralized tonic-clonic seizure when recovery of awareness followsrecovery of responsiveness, provided at least one of the key identifiers(e.g., loss of postural tone or diffuse increase in muscle tone orrhythmical body movements) have occurred.

In one embodiment, the epileptic event is classified as an atonicseizure when the following occur in a patient in a first, non-recumbentposition:

i) a body movement comprises a fall from the first, non-recumbentposition, wherein the fall is associated with a loss of responsiveness,a loss of awareness, or both; and

(ii) the patient shows a significant reduction in body movements below areference value after the fall, a significant reduction in muscle tonebelow a reference value after the fall, or both.

Typically, the significant reductions in body movements and/or muscletone commonly seen in atonic seizures are not caused by changes in heartor respiratory activity.

In one embodiment, the epileptic event is classified as tonic when thefollowing occur to a patient in a first, non-recumbent position: anincrease in muscle tone above a reference value, a loss ofresponsiveness, and an absence of generalized movements.

In a further embodiment, the epileptic event is classified as tonic whenrecovery of awareness follows recovery of responsiveness, provided ithas been associated with loss of responsiveness or awareness.

In one embodiment, the epileptic event is classified as a complexpartial seizure based upon a finding the patient's cardiac activity isassociated with impaired awareness and is not associated with a fall orat some point in time with generalized rhythmical body movements; andthe epileptic event is classified as a simple partial seizure based upona finding the patient's cardiac activity is not associated with impairedawareness and is not associated with generalized rhythmical bodymovements.

In one embodiment, the event is classified as syncope, when at least oneof the following occur: the body movement comprises a fall from anon-recumbent position and the fall is associated with a loss ofresponsiveness or a loss of awareness, and recovery of responsiveness orrecovery of awareness occurs immediately after the fall, or when thebody movement comprises a fall from a recumbent position, there ismarked decrease in heart rate or a brief transient cessation of heartbeats (asystole).

Epileptic events can be determined or classified in view of thepatient's body position. For example, an epileptic event when thepatient is in a decubitus position (lying down) may be determined froman observation of transient loss of muscle tone in antigravitatorymuscles (e.g., paraspinal; quadriceps), followed by transient increasein muscle tone in agonist and antagonist muscle groups (e.g., paraspinaland abdominal recti; quadriceps and hamstrings), which in turn isfollowed by generalized rhythmical muscle contractions (typically with afrequency of 3 Hz and/or 10-12 Hz at some time during the event).

For another example, an epileptic event when the patient is in a seatedposition may be determined using both electromyography (EMG) signals andaccelerometer signals.

The one or more of the first cardiac activity, the second cardiacactivity, the first body movement, the second body movement, theresponsiveness, and the awareness can be provided by any knowntechnique. In one embodiment, at least one of the first cardiac activityand the second cardiac activity is sensed by at least one of anelectrocardiogram (EKG), phonocardiogram (PKG), apexcardiography, bloodpressure monitor, and echocardiography. The body movement can be sensedby any known technique. In one embodiment, at least one of the firstbody movement and the second body movement is sensed by anaccelerometer, an inclinometer, an actigraph, an imaging system, adynamometer, a gyroscope, electromyography (EMG), or two or morethereof.

In certain circumstances, the method can make a false positivedetermination of an epileptic event, i.e., determine an epileptic eventbased on the signals and tests described above when no epileptic event(as may be determined using direct/invasive recording of electricalactivity at/near the epileptogenic zone, observation by a skilledpractitioner, or other techniques known to the person of ordinary skillin the art) occurred. In one embodiment, the method further comprisesreceiving an indication that the determined epileptic event was not anactual epileptic event. Such indications may include, but are notlimited to, the first body movement is a fall but the fall is notcharacteristic of an epileptic fall; the generalized body movements arenot rhythmical and bilaterally synchronous; the generalized bodymovement have a frequency substantially different from 3 Hz or avariable frequency; the generalized body movements change direction,pairs of agonist-antagonist muscles, and/or movements in differentdirections occur simultaneously in two or more joints; the change incardiac activity, cardiac activity morphology, cardiac spectralanalysis, apexcardiography, or echocardiography is not characteristic ofepileptic seizures.

Similarly, in one embodiment, the method further comprises receiving anindication of a false negative, i.e., an indication an epileptic eventoccurred but no determination thereof was made.

The indication may be based at least in part on input from the patient,a caregiver, or a medical professional, and/or on quantification orcharacterization of one or more body signals. The indication may beprovided at the time of the false determination or later.

A false determination (whether positive or negative) may render itappropriate to modify the body signals or analyses used in making futuredeterminations. In one embodiment, the method further comprises reducinga likelihood of a future determination of a false positive epilepticevent based at least in part on one or more of the first cardiacactivity, the first body movement, the responsiveness, the awareness,the second cardiac activity, the second body movement, the spectralanalysis of the second cardiac activity, or the spectral analysis of thesecond body movement, in response to the indication. In anotherembodiment, the method further comprises reducing a likelihood of afuture determination of a false negative epileptic event based at leastin part on one or more of the first cardiac activity, the first bodymovement, the responsiveness, the awareness, the second cardiacactivity, the second body movement, the spectral analysis of the secondcardiac activity, or the spectral analysis of the second body movement,in response to the indication.

When an epileptic event is determined, the method can further compriseone or more of logging the occurrence and/or time of occurrence of theseizure; providing a warning, alarm or alert to the patient, a caregiveror a health care provider; providing a therapy to prevent, abort, and/orreduce the severity of the seizure; assessing one or more patientparameters such as awareness or responsiveness during the seizure;assessing the severity of the seizure; identifying the end of theseizure; and assessing the patient's post-ictal impairment or recoveryfrom the seizure. “Recovery” is used herein to encompass a time afterseizure onset and/or seizure end when the patient's parameters arereturning to baseline. Other examples include, but are not limited to,logging one or more of a time of onset of the epileptic event, a time oftermination of the epileptic event, a severity of the epileptic event,an impact of the epileptic event, an interval between the epilepticevent and the most recent preceding epileptic event, an epileptic eventfrequency over a time window, an epileptic event burden over a timewindow, time spent in epileptic events over a time window, or a type ofepileptic event.

To reduce the rate of false positive detections or for other reasons, inone embodiment, the method further comprises

recording one or more of the patient's reference body movement ormovements, reference cardiac activity, reference responsiveness level,reference awareness level, reference cardiac activity, referencespectral analysis of the cardiac activity, or reference spectralanalysis of the body movement during one or more interictal activitiesat one or more times when the patient is not suffering an epilepticevent, to yield recorded data not associated with an epileptic event;defining one or more interictal activity reference characteristics fromthe recorded data; and overruling the determination of the epilepticevent based at least in part on finding the patient's first bodymovement, first cardiac activity, responsiveness level, awareness level,second cardiac activity, second body movement, spectral analysis of thesecond cardiac activity, and spectral analysis of the second bodymovement matches the one or more interictal event referencecharacteristics.

The interictal activities at one or more times when the patient is notsuffering an epileptic event can include different activities (e.g.,walking vs. running vs. swimming, etc.), and can alternatively or inaddition include the same activity at different times of day, week,month, or year, or under different external circumstances (e.g., walkingat sea level vs. walking at higher altitude, etc.).

The overruling of a determination of an epileptic event may be made withsome probability between zero and one. The overruling may be madeaccording to a permanent or semipermanent rule or on a case-by-casebasis. The references may be stored in a library on a per-patient,per-seizure type, or per-population basis.

In one embodiment, the overruling may involve the triggering of one ormore additional test(s). Such further triggering may allow more accuratedetermination of epileptic events.

Recording one or more of the patient's reference body movement ormovements, reference cardiac activity, reference responsiveness level,reference awareness level, reference cardiac activity, referencespectral analysis of the cardiac activity, or reference spectralanalysis of the body movement during epileptic event may allowoverruling of false negative or false positive determinations.

The body movement during one or more interictal activities can includeat least one of a movement of a part of the body (e.g., the eyes oreyelids), a movement of a limb (e.g., an arm), a movement of a part of alimb (e.g., a wrist), a direction of a movement, a velocity of amovement, a force of a movement, an acceleration of a movement, aquality of a movement, an aiming precision of a movement, or a purposeor lack thereof of a movement.

The likelihood of a patient suffering an epileptic event may change atdifferent times and/or under different conditions. In one embodiment, aplurality of interictal event reference characteristics are definedwhich differ from one another based on one or more of the time of day ofthe recording, the time of week of the recording, the time of month ofthe recording, the time of year of the recording, the type of activity,changes in the patient's body weight or body mass index, changes in thepatient's medication, changes in the patient's physical fitness or bodyintegrity, state of physical or mental health, mood level or changes inthe patient's mobility. Alternatively or in addition, a plurality ofinterictal event reference characteristics in a female patient can bedefined in reference to the menstrual cycle and/or to pregnancy.Alternatively or in addition, changes in the patient's environment maychange the likelihood of the patient suffering an epileptic event.

In a further embodiment, the overruling is based at least in part on oneor more of the plurality of interictal event reference characteristics.

Any characteristic of the one or more interictal events may beconsidered. In one embodiment, the one or more characteristics arepatterns or templates.

It may be desirable in certain embodiments to adapt at least one of areference value on one or more of the body movement, the cardiacactivity, the responsiveness level, the awareness level, the secondcardiac activity, the second body movement, and the spectral analysis ofcardiac activity or body movement, based upon one or more determinationsthat the specificity of past detections was above or below a specificitymeasure, the sensitivity of past detections was above or below asensitivity measure, the speed of detection defined as the time elapsedbetween the occurrence of the first body signal change indicative of theonset of the seizure and the issuance of the detection, the cost of thetherapy was below or above a cost measure, the patient's tolerance ofthe therapy was below an acceptable tolerance, the adverse effects wereabove an acceptable level, or the patient's disease state was below orabove a first disease state threshold. Positive predictive value ornegative predictive value may be used in addition to or instead ofspecificity or sensitivity.

As should be apparent, a single “threshold” can be mathematicallydefined in a number of ways that may be above or below a particularvalue of a particular parameter. For example, an elevated heart rate canbe defined, with equal validity, as a heart rate above a threshold inunits of beats/unit time or an interbeat interval below a threshold inunits of time. More than one “threshold” may be used to optimizespecificity, sensitivity or speed of detection.

For example, the method can further comprise determining one or more ofa specificity of past detections, a sensitivity of past detections, aspeed of past detections, a cost of a therapy for epileptic events, apatient's tolerance of a therapy for epileptic events, and a diseasestate of the patient; and loosening at least one constraint on one ormore of the body movement, the cardiac activity, the responsivenesstest, the awareness test, the second cardiac activity test, the secondbody movement test, and the spectral analysis of second cardiac activityor second body movement based upon one or more determinations that thespecificity of past detections was above a first specificity threshold,the sensitivity of past detections was below a first sensitivitythreshold, the speed of detection was below a first speed of detectionthreshold, the cost of the therapy was below a first cost threshold, thepatient's tolerance of the therapy was below a first tolerance threshold(i.e., the patient can tolerate more detections or actions performed inresponse to detections), and the patient's disease state was below afirst disease state threshold; or tightening the at least one constraintbased upon one or more determinations that the specificity of pastdetections was below a second specificity threshold, the sensitivity ofpast detections was above a second sensitivity threshold, the speed ofdetection was above an acceptable threshold for efficacy of therapy andsafety of the patient, the cost of the therapy was above a second costthreshold, the patient's tolerance of the therapy was above a secondtolerance threshold (i.e., the patient cannot tolerate more detectionsor actions performed in response to detections), and the patient'sdisease state was above a second disease state threshold.

In another embodiment, the invention can be used for the detection ofgeneralized tonic-clonic seizures. A “generalized tonic-clonic seizure”is used herein to refer to a primarily or secondarily generalizedseizure that features at least one tonic, clonic, or both tonic andclonic phase. Myoclonic seizures are included in this definition. Atonset or at some point during the generalized tonic-clonic seizure, atleast a majority of the body muscles or joints are involved. “Bodymuscle” is used herein to refer to those capable of moving joints, aswell as muscles of the eyes, face, orolaryngeal, pharyngeal, abdominal,and respiratory systems.

In one embodiment, the present invention relates to a method,comprising:

receiving at least two body signals selected from the group consistingof a signal relating to a first body movement, a signal relating to afirst cardiac activity, a responsiveness signal, an awareness signal, asignal relating to a second cardiac activity, a signal relating to asecond body movement, a spectral analysis signal relating to the secondcardiac activity, and a spectral analysis signal relating to the secondbody movement;

determining an occurrence of a generalized tonic-clonic epilepticseizure, the determination being based upon the correlation of at leasttwo features, at least one feature being of each of the at least twobody signals, wherein:

the feature of the first cardiac activity signal is an increase in thepatient's heart rate above an interictal reference value;

the feature of the first body movement signal is at least one of (i) anincrease in axial or limb muscle tone substantially above an interictalor exercise value for the patient, (ii) a decrease in axial muscle tonein a non-recumbent patient, below the value associated with a first,non-recumbent position, (iii) fall followed by an increase in bodymuscle tone, or (iv) a fall followed by generalized body movements;

the feature of the responsiveness signal is a decrease in the patient'sresponsiveness below an interictal reference value;

the feature of the awareness signal is a decrease in the patient'sawareness below an interictal reference value;

the feature of the second cardiac activity signal is a correlation withan ictal cardiac activity reference signal;

the feature of the second body movement signal is a correlation with anictal body movement reference signal;

the feature of the spectral analysis signal of the second cardiacactivity is a correlation with an ictal cardiac activity spectralanalysis reference signal; or

the feature of the spectral analysis signal of the second body movementis a correlation with an ictal body movement spectral analysis referencesignal;

and

performing a further action in response to the determination of theoccurrence of the epileptic event.

FIG. 11 depicts one embodiment of this method. FIG. 11 depicts areceiving step 1110, a determining step 1120, and a performing step1130.

In one embodiment, the correlation has a high absolute value and iseither positive or negative. E.g. the correlation may be positive, suchas with a value greater than 0.7, 0.75, 0.8, 0.85, 0.9, or 0.95, ornegative, such as with a value less than −0.7, −0.75, −0.8, −0.85, −0.9,or −0.95.

The further action may comprise one or more of logging the occurrenceand/or time of occurrence of the seizure; providing a warning, alarm oralert to the patient, a caregiver or a health care provider; providing atherapy to prevent, abort, and/or reduce the severity of the seizure;assessing one or more patient parameters such as awareness orresponsiveness during the seizure; assessing the severity of theseizure, identifying the end of the seizure; and assessing the patient'spost-ictal impairment or recovery from the seizure.

The various signals can be provided by any appropriate technique andtheir features referred to above can likewise be measured as a routinematter for the person of ordinary skill in the art having the benefit ofthe present disclosure. For example, in one embodiment, the correlationof the second cardiac activity signal with the ictal cardiac activityreference signal comprises a match to an ictal cardiac activitytemplate;

the correlation of the second body movement signal with the ictal bodymovement reference signal comprises a match to an ictal body movementtemplate;

the correlation of the spectral analysis signal of the second cardiacactivity with the ictal cardiac activity spectral analysis referencesignal comprises a match to an ictal cardiac activity spectral analysispattern or template; or

the correlation of the spectral analysis signal of the second bodymovement with the ictal body movement spectral analysis reference signalcomprises a match to an ictal body movement spectral analysis pattern ortemplate. Aspects of the signals and their features may include, amongothers, a body movement signal further comprising an indication of afall prior to the indication of the tonic or clonic activity.

In one embodiment, a tonic-clonic seizure can be further characterizedas secondarily generalized if the first body movement signal does notcomprise synchronous movement of all body muscles with equal amplitudeor velocity prior to an indication of tonic or clonic activity.

In one embodiment, the end of the generalized tonic-clonic epilepticseizure can be indicated when at least one of the body signals trendstoward an interictal reference value, range, or pattern of the bodysignal.

In one embodiment, the method further comprises indicating the beginningof a post-ictal period based upon the appearance of at least onepost-ictal feature of at least one the body signal, wherein:

the post-ictal feature of the first cardiac signal or the second cardiacsignal is a decrease in the patient's heart rate below an ictalreference value;

the post-ictal feature of the first body movement signal or the secondbody movement signal is a decrease in the patient's muscle tone ormovement below an ictal reference value;

the post-ictal feature of the responsiveness signal is an increase inthe patient's responsiveness above an ictal value and below aninter-ictal reference value; or

the post-ictal feature of the awareness signal is an increase in thepatient's awareness above an ictal value and below an inter-ictalreference value.

The term “post-ictal,” is not necessarily limited to the period of timeimmediately after the end of the primarily or secondarily generalizedtonic-clonic epileptic seizure and is not limited to this type ofseizure but also encompasses partial seizures (e.g., all complex andcertain simple partial and absence seizures). Rather, it refers to theperiod of time during which at least one signal has one or more featuresthat differs from the ictal and inter-ictal reference values thatindicates one or more of the patient's body systems are not functioningnormally (e.g., as a result of the seizure or of an injury sufferedduring the seizure) but are not exhibiting features indicative of aseizure.

In one embodiment, the end of the post-ictal period can be indicatedwhen each of the post-ictal features is outside the range of valuesassociated with the ictal and post-ictal states. In another embodiment,the end of the post-ictal period can be indicated when at least one ofthe post-ictal features is outside the range of values associated withthe ictal and post-ictal states. In this embodiment, the onset andtermination of the post-ictal period may be partial when all featureshave not returned to interictal reference values or complete when allfeatures have. This distinction (partial vs. complete) has importanttherapeutic (the patient may require treatment until all body signalshave fully recovered to inter-ictal values), safety (the patient'smortality and morbidity risks may remain increased until all body signalhave fully recovered to inter-ictal values) and predictive implications(the probability of occurrence of the next seizure and time to it(inter-seizure interval) may depend on recovery of one more body signalsto their interictal value.

It should also be borne in mind that different features are expected toreturn to their interictal reference values at different times. Forexample, from kinetic and brain electrical perspectives, a seizure canbe defined as having ended when abnormal movements and abnormal EEGcease. These events typically take place before the patient's heart ratereturns to baseline. Further, it may take a few minutes after abnormalmovements and abnormal EEG end for cognition and responsiveness toreturn to baseline; up to about 30 min for awareness to return tobaseline; and about 30-45 min for blood lactic acid concentration toreturn to baseline. Temporal relationships between changes in signalfeatures, and transitions from one state to another, are generallydescribed in U.S. patent application Ser. No. 12/896,525, filed Oct. 1,2010. Transitions may have quantifiable differences in location as well,e.g., the number of either brain sites or body organs in which thetransition has taken place may vary over time (e.g., an ictal changefirst occurring on the right mesiotemporal lobe, or a change in heartactivity at or near seizure onset followed by changes in metabolicindices.

In another embodiment, the present invention relates to the detection ofpartial seizures. In one embodiment, the present invention relates to amethod, comprising:

receiving at least two body signals selected from the group consistingof a signal relating to a first body movement, a signal relating to afirst cardiac activity, a responsiveness signal, an awareness signal, asignal relating to a second cardiac activity, a signal relating to asecond body movement, a spectral analysis signal relating to the secondcardiac activity, and spectral analysis signal relating to the secondbody movement; and

determining an occurrence of a partial epileptic seizure based upon acorrelation of two features, at least one feature being of each of theat least two body signals, wherein:

the feature of the first cardiac signal is a value outside an interictalreference value range;

the feature of the first body movement signal is a body movementassociated with a partial seizure;

the feature of the second cardiac activity signal is a correlation withan ictal cardiac activity reference signal;

the feature of the second body movement signal is a correlation with anictal body movement reference signal;

the feature of the spectral analysis signal of the second cardiacactivity is a correlation with an ictal cardiac activity spectralanalysis reference signal; or

the feature of the spectral analysis signal of the second body movementis a correlation with an ictal body movement spectral analysis referencesignal; and

performing a further action in response to the determination of theoccurrence of the epileptic event.

FIG. 12 depicts one embodiment of this method. FIG. 12 depicts areceiving step 1210, a determining step 1220, and a performing step1230.

The various signals can be provided by any appropriate technique andtheir features referred to above can likewise be measured as a routinematter for the person of ordinary skill in the art having the benefit ofthe present disclosure. For example, in one embodiment, the correlationof the second cardiac activity signal with the ictal cardiac activityreference signal comprises a match to an ictal cardiac activitytemplate;

the correlation of the second body movement signal with the ictal bodymovement reference signal comprises a match to an ictal body movementtemplate;

the correlation of the spectral analysis signal of the second cardiacactivity with the ictal cardiac activity spectral analysis referencesignal comprises a match to an ictal cardiac activity spectral analysispattern or template; or

the correlation of the spectral analysis signal of the second bodymovement with the ictal body movement spectral analysis reference signalcomprises a match to an ictal body movement spectral analysis pattern ortemplate.

Matches to patterns and templates are described in U.S. patentapplication Ser. No. 12/884,051, filed Sep. 16, 2010. A “match” shouldnot be construed as requiring a complete or perfect fit to a pattern ortemplate.

In one embodiment, the further action comprises one or more of loggingthe occurrence and/or time of occurrence of the seizure; providing awarning, alarm or alert to the patient, a caregiver or a health careprovider; providing a therapy to prevent, abort, and/or reduce theseverity of the seizure; assessing one or more patient parameters suchas awareness or responsiveness during the seizure; assessing theseverity of the seizure, identifying the end of the seizure; andassessing the patient's post-ictal impairment or recovery from theseizure.

Partial seizures generally result in body movements that do not includefalls.

The partial seizure can be classified as complex if at least one of thefeatures of the awareness signal is a decrease in the patient'sawareness below its reference value, or as (ii) simple if there is nodecrease in the patient's awareness below its reference value, or ifthere is a decrease in the patient's responsiveness but awarenessremains at an interictal value.

In one embodiment, the end of the partial epileptic seizure can beindicated when at least one of the features of the respective bodysignals is outside the range of values associated with the ictal statefor that body signal. In another embodiment, the end of the partialepileptic seizure can be indicated when each of the features of therespective body signals trends toward an interictal reference value,range, or pattern of the body signal.

In one embodiment, the method further comprises indicating the beginningof a post-ictal period when at least one of the body signals is outsidethe range of values associated with the ictal and inter-ictal states forthat body signal, wherein:

the post-ictal feature of the cardiac signal is a heart rate outside therange of values associated with the ictal state;

the post-ictal feature of the body movement signal is a change in thepatient's movement outside the ictal range of values;

the post-ictal feature of the responsiveness signal is an increase inthe patient's responsiveness above an ictal reference value butremaining below an inter-ictal reference value; and

the post-ictal feature of the awareness signal is an increase in thepatient's awareness above an ictal reference value but remaining belowan inter-ictal reference value.

In one embodiment, the end of the post-ictal period can be indicatedwhen at least one of the post-ictal features is absent from itsrespective body signal.

In one embodiment, such responsive action(s) may be taken if the ictalor postictal state's severity exceeds a threshold, e.g., the 90thpercentile values for a patient.

Various responsive actions, such as warning, logging, and treating,among others, are generally described in U.S. patent application Ser.No. 12/896,525, filed Oct. 1, 2010. A warning may be graded, e.g., ayellow light for a mild seizure, a red light for a severe one. Treatingcan comprise providing supporting treatment (e.g., fluids, oxygen).

Seizure severity indices may be calculated and stored by appropriatetechniques and apparatus. More information on seizure severity indicesis available in U.S. patent application Ser. No. 13/040,996, filed Mar.4, 2011.

In one embodiment, the present invention relates to a system,comprising:

-   -   at least one sensor configured to receive at least one of a        signal relating to a first cardiac activity from a patient, a        signal relating to a first body movement from the patient, a        responsiveness signal from the patient, an awareness signal from        the patient, a signal relating to a second cardiac activity of        the patient, and a signal relating to a second body movement of        the patient;    -   a detection unit configured to receive the at least one signal        from the at least one sensor and determine an occurrence of an        epileptic event; and    -   an action unit configured to receive an indication of the        occurrence of the epileptic event from the detection unit and        perform at least one of logging the occurrence and/or time of        occurrence of the epileptic event; providing a warning, alarm or        alert to the patient, a caregiver or a health care provider;        providing a therapy to prevent, abort, and/or reduce the        severity of the epileptic event; assessing one or more patient        parameters such as awareness or responsiveness during the        epileptic event; assessing the severity of the epileptic event,        identifying the end of the epileptic event; and assessing the        patient's post-ictal impairment or recovery from the epileptic        event.

The system can further comprise other units. For example, the system cancomprise a spectral analysis unit configured to generate at least onespectral analysis signal from the signal relating to the second cardiacactivity and/or the signal relating to the second body movement. In thisembodiment, it may be desirable for the detection unit to be furtherconfigured to receive the at least one spectral analysis signal from thespectral analysis unit.

Although not limited to the following, exemplary systems capable ofimplementing embodiments of the present invention are generallydiscussed below and in U.S. patent application Ser. No. 12/896,525,filed Oct. 1, 2010.

FIG. 1A depicts a stylized system comprising an external unit 145 acapable of receiving, storing, communicating, and/or calculatinginformation relating a patient's epileptic events. The system shown inFIG. 1A also includes at least one sensor 212. The sensor 212 may beconfigured to receive cardiac activity data, body movement data,responsiveness data, awareness data, or other data from the patient'sbody. A lead 211 is shown allowing communication between the sensor 212and the external unit 145 a.

FIG. 1B depicts a stylized implantable medical system (IMD) 100, similarto that shown in FIG. 1 of U.S. patent application Ser. No. 12/896,525,filed Oct. 1, 2010, and discussed therein.

FIG. 2 is shown and generally described in U.S. patent application Ser.No. 12/896,525, filed Oct. 1, 2010. As is apparent to the person ofordinary skill in the art, the neurological signal module 275 is capableof collecting neurological data and providing the collected neurologicaldata to a detection module 285.

In other embodiments (not shown), other types of signals may becollected and provided to the detection module 285.

FIG. 3A and FIG. 3B are generally as shown and described in U.S. patentapplication Ser. No. 12/896,525, filed Oct. 1, 2010. The ocular signalunit 318 is generally capable of providing at least one ocular signal(e.g., pupil dilation, pupillary hippus, blinking, etc.).

FIG. 3B herein also depicts an awareness determination unit 3020 j.

In addition, a device can comprise other signal modules. For example, itmay comprise a metabolic signal module, which can comprise a bloodparameter signal unit capable of providing at least one blood parametersignal (e.g., blood glucose, blood pH, blood gas, etc). Alternatively orin addition, the metabolic signal module can comprise a hormone signalunit capable of providing at least one hormone signal.

A detection module 285, as shown in FIG. 3C, is generally described inU.S. patent application Ser. No. 12/896,525, filed Oct. 1, 2010.

The above methods may be performed by a computer readable programstorage device encoded with instructions that, when executed by acomputer, perform the method described herein.

All of the methods and apparatuses disclosed and claimed herein may bemade and executed without undue experimentation in light of the presentdisclosure. While the methods and apparatus of this invention have beendescribed in terms of particular embodiments, it will be apparent tothose skilled in the art that variations may be applied to the methodsand apparatus and in the steps, or in the sequence of steps, of themethod described herein without departing from the concept, spirit, andscope of the invention, as defined by the appended claims. It should beespecially apparent that the principles of the invention may be appliedto selected cranial nerves other than, or in addition to, the vagusnerve to achieve particular results in treating patients havingepilepsy, depression, or other medical conditions.

What is claimed is:
 1. A method, comprising: receiving a respiratorysignal indicative of the patient's respiration; determining at least onerespiratory feature from the respiratory signal; receiving a kineticsignal indicative of the patient's kinetic activity; determining atleast one kinetic feature from the kinetic signal; detecting anepileptic seizure based on the at least one respiratory feature and theat least one kinetic feature; and performing a further action inresponse to said detecting, wherein said further action comprises one ormore of: logging the occurrence of the epileptic seizure; logging thetime of occurrence of the epileptic the seizure; logging the date ofoccurrence of the epileptic seizure; providing at least one of awarning, alarm or alert to the patient, a caregiver or a health careprovider; providing a therapy to prevent, abort, reduce the severity, orreduce the duration of the epileptic seizure; assessing at least one ofthe awareness or responsiveness of the patient during the epilepticseizure; assessing the severity of the epileptic seizure; determiningthe end of the epileptic seizure; determining the beginning of apost-ictal period; determining the end of a post-ictal period; andassessing the patient's post-ictal impairment or recovery from theepileptic seizure.
 2. The method of claim 1, wherein determining atleast one respiratory feature comprises determining at least one of arespiration rate, a rate of change of a respiration rate, a respirationfrequency, a respiratory rhythm, a tidal volume, a minute volume, arespiratory wave morphology, a respiratory sound, an end-tidal CO2concentration, an intercostal EMG value, a diaphragmatic EMG value, achest wall motion value, an abdominal wall motion value, a change inrespiration rate, a rate of change in respiration rate, an apneaepisode, a hypopnea episode, a hyperpnea episode, and an airflowvelocity.
 3. The method of claim 2, wherein detecting an epilepticseizure based on the at least one respiratory feature comprisesdetecting a change in at least one of the patient's respiration rate,frequency, rhythm, tidal volume, or minute volume to a value outside aninterictal reference value range.
 4. The method of claim 3, whereindetermining the end of a post-ictal period is based on at least one ofthe patient's respiration rate, frequency, tidal volume or minute volumereturning to a value within an interictal reference value range.
 5. Themethod of claim 1, wherein determining at least one kinetic featurecomprises determining at least one of a direction of movement, a speedof movement, a frequency of movement, an acceleration in one, two orthree dimensions, a trajectory of movement, a pattern of movement, aquality of a movement, a force of contraction of a muscle, a bodyposture, a body orientation, a body position, a muscle tone an agonist-to-antagonist muscle tone relation, a gait, and a fall.
 6. The method ofclaim 1, wherein detecting an epileptic seizure is based on the temporalrelationship between the at least one respiratory feature and the atleast one kinetic feature.
 7. The method of claim 1, wherein detectingan epileptic seizure is based on changes in at least one of therespiratory feature and the kinetic feature.
 8. The method of claim 1,wherein determining at least one respiratory feature comprisesdetermining at least one of a respiration rate, a respiratory rhythm, atidal volume, a minute volume, and a respiration pattern.
 9. The methodof claim 8, wherein detecting an epileptic seizure is based on at leastone of a respiratory rate, a respiratory rhythm, a tidal volume, aminute volume, and a respiration pattern outside of an interictalreference value range.
 10. The method of claim 1, wherein detecting saidepileptic seizure is based on determining an apnea episode followed by ahypopnea episode.
 11. The method of claim 1, wherein determining the endof the epileptic seizure comprises determining an increase in at leastone of the patient's respiratory rate, tidal volume, and minute volume.12. The method of claim 1, wherein determining the end of the epilepticseizure comprises determining that at least one of the patient'srespiratory rate, respiratory rhythm, tidal volume, minute volume, andrespiratory pattern has returned to an interictal reference value range.13. The method of claim 1, further comprising determining the beginningof a post-ictal period based at least in part on determining, afterdetecting an epileptic seizure, a change in at least one of thepatient's respiratory rate, respiratory rhythm, frequency, tidal volume,and minute volume to a value outside an ictal reference value range. 14.The method of claim 1, further comprising: administering at least one ofa responsiveness test and an awareness test to the patient; anddetermining a result for said at least one of a responsiveness test andan awareness test; wherein detecting an epileptic seizure is dependenton said patient failing said at least one of a responsiveness test andan awareness test.
 15. The method of claim 1, further comprising:administering at least one of a responsiveness test and an awarenesstest to the patient; determining a result for said at least one of aresponsiveness test and an awareness test; and at least one ofclassifying said epileptic seizure or identifying a false positivedetection based at least in part on the result of said at least one of aresponsiveness test and an awareness test.
 16. The method of claim 1,further comprising classifying the seizure as at least one of: anepileptic seizure; a non-epileptic seizure; a primarily generalizedseizure; a secondarily generalized seizure; a complex partial seizure; asimple partial seizure.
 17. A method, comprising: receiving arespiratory signal indicative of the patient's respiration; determiningat least one respiratory feature from the respiratory signal; receivinga cardiac signal indicative of the patient's cardiac activity;determining at least one cardiac feature from the cardiac signal;detecting an epileptic seizure based on the at least one respiratoryfeature and the at least one cardiac feature; and performing a furtheraction in response to said detecting, wherein said further actioncomprises one or more of: logging the occurrence of the epilepticseizure; logging the time of occurrence of the epileptic the seizure;logging the date of occurrence of the epileptic seizure; providing atleast one of a warning, alarm or alert to the patient, a caregiver or ahealth care provider; providing a therapy to prevent, abort, reduce theseverity, or reduce the duration of the epileptic seizure; assessing atleast one of the awareness or responsiveness of the patient during theepileptic seizure; assessing the severity of the epileptic seizure;determining the end of the epileptic seizure; and assessing thepatient's post-ictal impairment or recovery from the epileptic seizure.18. A method, comprising: receiving a respiratory signal indicative ofthe patient's respiration; determining at least one respiratory featurefrom the respiratory signal; receiving at least one of cardiac signalindicative of the patient's cardiac activity and a kinetic signalindicative of a body movement of the patient; determining at least oneof a cardiac feature from the cardiac signal and a kinetic feature fromthe kinetic signal; detecting an epileptic seizure based on the at leastone respiratory feature and at least one of said cardiac feature andsaid kinetic feature; and performing a further action in response tosaid detecting, wherein said further action comprises one or more of:logging the occurrence of the epileptic seizure; logging the time ofoccurrence of the epileptic the seizure; logging the date of occurrenceof the epileptic seizure; providing at least one of a warning, alarm oralert to the patient, a caregiver or a health care provider; providing atherapy to prevent, abort, reduce the severity, or reduce the durationof the epileptic seizure; assessing at least one of the awareness orresponsiveness of the patient during the epileptic seizure; assessingthe severity of the epileptic seizure; determining the end of theepileptic seizure; and assessing the patient's post-ictal impairment orrecovery from the epileptic seizure.
 19. A system, comprising: at leastone respiratory sensor for sensing a respiratory signal indicative ofthe patient's respiration; at least one kinetic sensor to sense a bodymovement signal of the patient; at least one feature determination unitfor determining at least one respiratory feature from the respiratorysignal and at least one kinetic feature from the body movement signal;at least one seizure detection unit configured to detect the occurrenceof an epileptic seizure based on the respiratory feature and the kineticfeature; and an action unit configured to receive an indication of saidoccurrence of said epileptic seizure from said detection unit andperform at least one of logging the occurrence of the epileptic seizure;logging the time of occurrence of the epileptic the seizure; logging thedate of occurrence of the epileptic seizure; providing at least one of awarning, alarm or alert to the patient, a caregiver or a health careprovider; providing a therapy to prevent, abort, reduce the severity, orreduce the duration of the epileptic seizure; assessing at least one ofthe awareness or responsiveness of the patient during the epilepticseizure; assessing the severity of the epileptic seizure; determiningthe end of the epileptic seizure; and assessing the patient's post-ictalimpairment or recovery from the epileptic seizure.
 20. The system ofclaim 19, further comprising at least one of a cardiac sensor forsensing a cardiac signal indicative of the patient's cardiac activity,an awareness determination unit for determining the patient's awareness,and a responsiveness determination unit for determining the patient'sresponsiveness.